scholarly journals Barrel Instability in Binary Asteroids

2021 ◽  
Vol 2 (6) ◽  
pp. 231
Author(s):  
Matija Ćuk ◽  
Seth A. Jacobson ◽  
Kevin J. Walsh
Keyword(s):  
Numerical Simulations ◽  
Rotational State ◽  
Large Set ◽  
Binary Asteroids ◽  
High Eccentricity ◽  
Earth Asteroid ◽  
Prolate Shape ◽  
Planetary Satellites ◽  
Synchronous Rotation ◽  
Secondary Line

Abstract Most close-in planetary satellites are in synchronous rotation, which is usually the stable end-point of tidal despinning. Saturn’s moon Hyperion is a notable exception by having a chaotic rotation. Hyperion’s dynamical state is a consequence of its high eccentricity and its highly prolate shape. As many binary asteroids also have elongated secondaries, chaotic rotation is expected for moons in eccentric binaries, and a minority of asteroidal secondaries may be in that state. The question of secondary rotation is also important for the action of the binary Yarkovsky–O’Keefe–Radzievskii–Paddack (BYORP) effect, which can quickly evolve orbits of synchronous (but not nonsynchronous) secondaries. Here we report results of a large set of short numerical simulations which indicate that, apart from synchronous and classic chaotic rotation, close-in irregularly shaped asteroidal secondaries can occupy an additional, intermediate rotational state. In this “barrel instability” the secondary slowly rolls along its long axis, while the longest axis is staying largely aligned with the primary–secondary line. This behavior may be more difficult to detect through lightcurves than a fully chaotic rotation, but would likewise shut down BYORP. We show that the binary’s eccentricity, separation measured in secondary’s radii and the secondary’s shape are all important for determining whether the system settles in synchronous rotation, chaotic tumbling, or barrel instability. We compare our results for synthetic asteroids with known binary pairs to determine which of these behaviors may be present in the near-Earth asteroid binary population.

"Barrel Instability" for Elongated Secondaries in Binary Asteroids

2020 ◽  
Author(s):  
Matija Cuk ◽  
Seth Jacobson ◽  
Kevin Walsh
Keyword(s):  
Binary Systems ◽  
Spin Orbit Coupling ◽  
Spin Orbit ◽  
Binary Asteroids ◽  
High Eccentricity ◽  
Prolate Shape ◽  
Planetary Satellites ◽  
Synchronous Rotation ◽  
Secondary Line ◽  
Theoretical Results

<p>Most close-in planetary satellites are in synchronous rotation, which is usully the stable end-point of tidal despinning. Saturn's moon Hyperion is a notable exception by having a chaotic rotation. Hyperion's dynamical state is a consequence of its high eccentricity and its highly prolate shape (Wisdom et al. 1984). As many binary asteroids also have elongated secondaries, chaotic rotation is expected for moons in eccentric binaries (Cuk & Nesvorny 2010), and a minority of asteroidal secondaries may be in that state (Pravec et al. 2016). The question of the secondary's rotation is importrant for the action of the BYORP effect, which can quickly evolve orbits of synchrnous (but not non-synchronous) secondaries (Cuk & Burns 2005). Here we report preliminary numerical simulations which indicate that in binary systems with a large secondary and significant spin-orbit coupling a different kind of non-synchronous rotation may arise. In this "barrel instability" the secondary slowly rolls along its long axis, while the longest diameter is staying largelly aligned with the primary-secondary line. This behavior  may be more difficult to detect through lightcurves than a fully chaotic rotation, but would likewise shut down BYORP. Unlike fully chaotic rotation, barrel instability can happen even at low eccentricties. In our presentation we will discuss our theoretical results and their implications for the evolution of binary asteroids, such as the Didymos-Dimorphos pair.</p>

scholarly journals Rankine-type cylinders having zero wave resistance in infinitely deep flows

2020 ◽  
Vol 85 (3) ◽  
pp. 343-364
Author(s):  
Julien Dambrine ◽  
Evi Noviani ◽  
Morgan Pierre
Keyword(s):  
Numerical Simulations ◽  
Uniform Flow ◽  
Wave Resistance ◽  
Large Set

Abstract We prove the existence of a family of immersed obstacles that have zero wave resistance in the context of the 2D Neumann–Kelvin problem. We first build a waveless potential by superposing a source and a sink in a uniform flow for an appropriate choice of parameters. The obstacle is obtained by a combination of streamlines of the waveless potential. Numerical simulations show that the construction is valid for a large set of parameters.

scholarly journals Revisiting migration in a disc cavity to explain the high eccentricities of warm Jupiters

2020 ◽  
Vol 500 (2) ◽  
pp. 1621-1632
Author(s):  
Florian Debras ◽  
Clément Baruteau ◽  
Jean-François Donati
Keyword(s):  
Numerical Simulations ◽  
Working Mechanism ◽  
High Eccentricity ◽  
A Value

ABSTRACT The distribution of eccentricities of warm giant exoplanets is commonly explained through planet–planet interactions, although no physically sound argument favours the ubiquity of such interactions. No simple, generic explanation has been put forward to explain the high mean eccentricity of these planets. In this paper, we revisit a simple, plausible explanation to account for the eccentricities of warm Jupiters: migration inside a cavity in the protoplanetary disc. Such a scenario allows to excite the outer eccentric resonances, a working mechanism for higher mass planets, leading to a growth in the eccentricity while preventing other, closer resonances to damp eccentricity. We test this idea with diverse numerical simulations, which show that the eccentricity of a Jupiter-mass planet around a Sun-like star can increase up to ∼0.4, a value never reached before with solely planet–disc interactions. This high eccentricity is comparable to, if not larger than, the median eccentricity of warm Saturn- to Jupiter-mass exoplanets. We also discuss the effects such a mechanism would have on exoplanet observations. This scenario could have strong consequences on the disc lifetime and the physics of inner disc dispersal, which could be constrained by the eccentricity distribution of gas giants.

scholarly journals Revisiting migration in a disc cavity to explain the high eccentricities of warm Jupiters

2020 ◽  
Author(s):  
Florian Debras ◽  
Clément Baruteau ◽  
Jean-François Donati
Keyword(s):  
Numerical Simulations ◽  
Working Mechanism ◽  
High Eccentricity ◽  
A Value

<p>The distribution of eccentricities of warm giant exoplanets is commonly explained through planet--planet interactions, although no physically sound argument favours the ubiquity of such interactions. No simple, generic explanation has been put forward to explain the high mean eccentricity of these planets.</p> <p>In this talk, I will present a simple, plausible explanation to account for the eccentricities of warm Jupiters: migration inside a cavity in the protoplanetary disc. Such a scenario allows to excite the outer eccentric resonances, a working mechanism for higher mass planets, leading to a growth in the eccentricity while preventing the drag from non-corotating eccentric gas to damp eccentricity. This idea is tested with diverse numerical simulations, which show that the eccentricity of a Jupiter-mass planet around a Sun-like star can increase up and settle to $\sim 0.4$, a value never reached before with solely planet--disc interactions. This high eccentricity is comparable to, if not larger than, the median eccentricity of warm Saturn- to Jupiter-mass exoplanets.</p> <p>I will finally discuss the effects such a scenario would have on observations, notably on the discs lifetime and the physics of inner disc dispersal.</p>

scholarly journals Shear Driven Turbulence and Coherent Structures in Solar Surface Simulations

2008 ◽  
Vol 4 (S252) ◽  
pp. 451-461 ◽  
Author(s):  
F. Kupka
Keyword(s):  
High Resolution ◽  
Boundary Conditions ◽  
Numerical Simulations ◽  
Observational Data ◽  
Coherent Structures ◽  
Solar Surface ◽  
Large Set ◽  
Mode Excitation

AbstractNumerical simulations of convection near the solar surface are now advanced enough to reproduce both a large set of observational data and provide tests for convection models. We discuss the role of coherent structures in models of solar p-mode excitation, for which the analysis of numerical simulations has provided key inputs in the modelling. The robustness of these simulations is shown by a comparison illustrating the influence of boundary conditions on ensemble averaged quantities. In a concluding example advanced high resolution simulations are shown to resolve the onset of shear driven turbulence generated by up- and downflow structures.

COLLECTIVE MODES OF THREE COUPLED RELAXATION OSCILLATORS: THE INFLUENCE OF DETUNING

1999 ◽  
Vol 09 (10) ◽  
pp. 1969-1981 ◽  
Author(s):  
DIETMAR RUWISCH ◽  
MATHIAS BODE ◽  
DENIS VOLKOV ◽  
EVGENII VOLKOV
Keyword(s):  
Experimental Data ◽  
Numerical Simulations ◽  
Slow Variable ◽  
Phase Relations ◽  
Collective Modes ◽  
Large Set ◽  
Synchronous Oscillation ◽  
Relaxation Oscillators ◽  
Basic Set ◽  
Periodic Attractors

The dynamics of a ring of three relaxation oscillators symmetrically coupled in the slow variable is considered both experimentally and by means of numerical simulations. It is shown that apart from the synchronous oscillation the basic set of periodic attractors typical for identical oscillators is not essentially affected by a small detuning. However, detuning creates a large set of new collective modes which are characterized by larger system periods and a variety of phase relations between the oscillators. Comparisons of the experimental data with different oscillator models reveal that the results do not crucially depend on the specific features of the models and possible experimental uncertainties.

scholarly journals Spin dynamics of close-in planets exhibiting large transit timing variations

2017 ◽  
Vol 605 ◽  
pp. A37 ◽  
Author(s):  
J.-B. Delisle ◽  
A. C. M. Correia ◽  
A. Leleu ◽  
P. Robutel
Keyword(s):  
Numerical Simulations ◽  
Orbital Period ◽  
Spin Dynamics ◽  
Rotation Period ◽  
Tidal Dissipation ◽  
Link Type ◽  
Spin Evolution ◽  
Synchronous Rotation ◽  
The Mean ◽  
Good Probe

We study the spin evolution of close-in planets in compact multi-planetary systems. The rotation period of these planets is often assumed to be synchronous with the orbital period due to tidal dissipation. Here we show that planet-planet perturbations can drive the spin of these planets into non-synchronous or even chaotic states. In particular, we show that the transit timing variation (TTV) is a very good probe to study the spin dynamics, since both are dominated by the perturbations of the mean longitude of the planet. We apply our model to KOI-227 b and Kepler-88 b, which are both observed undergoing strong TTVs. We also perform numerical simulations of the spin evolution of these two planets. We show that for KOI-227 b non-synchronous rotation is possible, while for Kepler-88 b the rotation can be chaotic.

Ab initio band theory approach to electron energy loss near edge structures

1988 ◽  
Vol 46 ◽  
pp. 506-507
Author(s):  
Xudong Weng ◽  
O.F. Sankey ◽  
Peter Rez
Keyword(s):  
Ab Initio ◽  
Local Density ◽  
Interpolation Method ◽  
Atomic Orbital ◽  
Plane Waves ◽  
Large Set ◽  
Theory Approach ◽  
Band Theory ◽  
Atomic Orbitals ◽  
Pseudopotential Calculations

Single electron band structure techniques have been applied successfully to the interpretation of the near edge structures of metals and other materials. Among various band theories, the linear combination of atomic orbital (LCAO) method is especially simple and interpretable. The commonly used empirical LCAO method is mainly an interpolation method, where the energies and wave functions of atomic orbitals are adjusted in order to fit experimental or more accurately determined electron states. To achieve better accuracy, the size of calculation has to be expanded, for example, to include excited states and more-distant-neighboring atoms. This tends to sacrifice the simplicity and interpretability of the method.In this paper. we adopt an ab initio scheme which incorporates the conceptual advantage of the LCAO method with the accuracy of ab initio pseudopotential calculations. The so called pscudo-atomic-orbitals (PAO's), computed from a free atom within the local-density approximation and the pseudopotential approximation, are used as the basis of expansion, replacing the usually very large set of plane waves in the conventional pseudopotential method. These PAO's however, do not consist of a rigorously complete set of orthonormal states.

Molecular Views of Ice-Embedded Lumbricus Terrestris Erythrocruorin Obtained By Invariant Classification

1990 ◽  
Vol 48 (1) ◽  
pp. 450-451
Author(s):  
Michael schatz ◽  
Joachim Jäger ◽  
Marin van Heel
Keyword(s):  
Image Interpretation ◽  
Lumbricus Terrestris ◽  
Reference Image ◽  
Large Set ◽  
Multivariate Statistical ◽  
Data Set ◽  
Low Contrast ◽  
Negative Stain ◽  
Reference Images ◽  
Statistical Resolution

Lumbricus terrestris erythrocruorin is a giant oxygen-transporting macromolecule in the blood of the common earth worm (worm "hemoglobin"). In our current study, we use specimens (kindly provided by Drs W.E. Royer and W.A. Hendrickson) embedded in vitreous ice (1) to avoid artefacts encountered with the negative stain preparation technigue used in previous studies (2-4).Although the molecular structure is well preserved in vitreous ice, the low contrast and high noise level in the micrographs represent a serious problem in image interpretation. Moreover, the molecules can exhibit many different orientations relative to the object plane of the microscope in this type of preparation. Existing techniques of analysis requiring alignment of the molecular views relative to one or more reference images often thus yield unsatisfactory results.We use a new method in which first rotation-, translation- and mirror invariant functions (5) are derived from the large set of input images, which functions are subsequently classified automatically using multivariate statistical techniques (6). The different molecular views in the data set can therewith be found unbiasedly (5). Within each class, all images are aligned relative to that member of the class which contributes least to the classes′ internal variance (6). This reference image is thus the most typical member of the class. Finally the aligned images from each class are averaged resulting in molecular views with enhanced statistical resolution.

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